Reaction of thioamides with 2,3-dichloro-1,4-naphthoquinone. A novel synthesis of naphtho[2,3-d]thiazole-4,9-diones

Abstract

The reaction of thioamide II with 2,3-dichloro-1,4-naphthoquinone (I) in ethanol gave naptho[2,3-d]thiazole-4,9-diones (IV). The intermediates, 2-thioamido-3-chloro-1,4-naphthoquinones III were also isolated from the reaction medium and could be separately transformed to IV by further boiling in aqueous ethanol containing bicarbonate. The reaction of thiosemicarbazide with I under similar conditions gave naphtho[2,3-e]-2-amino-4H-1,3,4-thiadiazine-5,10-dione (VII).